The invention relates to a display device comprising a first substrate which is provided with electron-generating means for generating electron beams towards a second substrate which is parallel to the first substrate and is provided with fluorescent means.
Display devices of this type are used, for example in monitors or in video apparatus at places where a cathode ray tube is not very well usable.
The first substrate may be a glass substrate provided with, for example field emitters as electron-generating means, but also, for example a silicon substrate in which field emitters or, for example cold cathodes based on avalanche multiplication (pn emitters) are realised as electron-generating means. Examples of field emitters and their manufacture are given in U.S. Pat. No. 3,812,559, while a description of pn emitters can be found in U.S. Pat. No. 4,303,930. A "diamond" emitter may be used alternatively.
The second substrate usually comprises phosphors as fluorescent means which are patterned and towards which the electrons are accelerated.
Notably when larger display devices are manufactured, various problems present themselves. When electrons from a given electron-generating area (which may be a single cathode or a group of emitters) are applied to each phosphor area on the second substrate, these areas must be aligned very accurately with respect to each other. Moreover, the substrates on which the pattern of these electron-generating areas are realised are usually restricted to maximum dimensions, for example because the diameter is restricted to, for example 15 cm for glass plates on which a field emitter matrix is realised, or to approximately 5 cm for semiconductor substrates in which cold cathodes are realised so as to obtain a satisfactory yield.
A second problem which may present itself is that electrons which land on the phosphor area are elastically scattered and impinge upon an adjacent area which emits light of a different colour. This gives rise to colour contamination.